Mesa and butte

Photo by: dpa

Spanish
explorers in the mid-sixteenth century ranged over the American
Southwest. They had come north from Mexico, looking for gold and gems and
the legendary Seven Cities of Cibola (pronounced SEE-bow-lah), allegedly
filled with such treasures. In their quest, they found neither gold nor
riches. They did, however, become the first Europeans to view the
geological wonders of the area, and they were amazed at what they saw.

Among the canyons, plateaus, and rock towers and arches, the explorers saw
landforms that appeared plateaulike, only smaller and isolated. They
called these geologic features mesas (pronounced MAY-suz), which means
table in Spanish, because the explorers thought the landforms resembled
tables with their smooth, flat tops and sides that drop away steeply.
Populating the spare, arid (dry) landscape of the area along with mesas
were still smaller landforms that had a similar appearance. At the
beginning of the nineteenth century, the word butte (pronounced BYOOT) was
coined from the French word meaning mound or hillock to describe these
solitary landforms.

The shape of the land

A mesa is an isolated, flat-topped hill or mountain with steep sides that
is smaller in area than a plateau. A butte is also a flat-topped hill with
steep sides, though smaller in area than a mesa. Definitions of the
surface areas of mesas and buttes vary. One source states that a mesa has
a surface area of less than 4 square miles (10 square kilometers), while a
butte has a surface area less than 11,250 square feet (1,000 square
meters). Another source states that the surface area of a mesa is larger
than 1 square mile (2.59 square kilometers); the surface area of a butte
is smaller than that dimension. Some simply define a mesa as a

Junction Butte in Canyon-lands National Park, Utah. Part of the
Colorado Plateau, the landscape of sedimentary sandstone in this
area was eroded into countless canyons, mesas, and buttes by the
Colorado River and its tributaries
.
PHOTOGRAPH REPRODUCED BY PERMISSION OF THE

CORBIS CORPORATION

.

landform that is wider than it is high and a butte as one that is higher
than it is wide.

A mesa's and butte's characteristic shape—flat top
and clifflike sides—is due to the layers of rock forming them.
These landforms are most often composed of sedimentary rock, formed by the
accumulation and compression of sediment (which may consist of rock
fragments, remains of microscopic organisms, and minerals). This type of
rock covers more than 75 percent of Earth's land surface. Most
sedimentary rocks occur in layers, called strata, that are mostly
horizontal or flat when first formed. Forces within Earth that rupture the
surface to form volcanoes, mountains, plateaus, and many other
topographical features (physical features on the planet's surface),
may later cause these layers to tip, fold, warp, or fracture.

The top layer of a mesa and a butte is a hardened layer of rock that is
resistant to erosion, which is the gradual wearing away of Earth surfaces
through the action of wind and water. Sometimes this top layer, called the
cap rock, is not sedimentary rock but is cooled and hardened lava that had
spread out across the landscape in repeated flows from fissures or cracks
in
the ground. Beneath this flat protective cap of rock are horizontal
layers of softer sedimentary rock. To varying degrees, these layers are
not as resistant to erosion.

These landforms are found in arid and semiarid regions. Arid regions are
defined as those that receive less than 10 inches (25 centimeters) of rain
per year; semiarid regions receive 10 to 20 inches (25 to 50 centimeters)
of rain per year. Precipitation in these regions often comes in the form
of sudden, heavy rainfalls. Because water evaporates quickly in these
normally dry environments, plants and other ground cover are scarce. Left
exposed to the action of running water, the bare sides of the softer rock
layers of mesas and buttes are eroded away over time. The base of these
landforms is often gently sloped, contrasting with the almost-vertical
sides leading down from the top. Rock material that has been eroded from
the sides is carried downward, forming this sloping base.

Mesa and butte: Words to Know

Canyon:

A narrow, deep, rocky, and steep-walled valley carved by a
swift-moving river.

Cap rock:

Erosion-resistant rock that overlies other layers of less-resistant
rock.

Cliff:

A high, steep face of rock.

Crust:

The thin, solid, outermost layer of Earth.

Erosion:

The gradual wearing away of Earth surfaces through the action of wind
and water.

Fault:

A crack or fracture in Earth's crust along which rock on one
side has moved relative to rock on the other.

Pinnacle:

A tall, slender tower or spire of rock.

Plateau:

A relatively level, large expanse of land that rises some 1,500 feet
(457 meters) or more above its surroundings and has at least one steep
side.

Plates:

Large sections of Earth's lithosphere that are separated by
deep fault zones.

Plate tectonics:

The geologic theory that Earth's crust is composed of rigid
plates that "float" toward or away from each other,
either directly or indirectly, shifting continents, forming mountains
and new ocean crust, and stimulating volcanic eruptions.

Sedimentary rock:

Rock formed by the accumulation and compression of sediment, which may
consist of rock fragments, remains of microscopic organisms, and
minerals.

Strata:

Layers in a series of sedimentary rocks.

Forces and changes: Construction and destruction

Mesas and buttes do not arise as completed landforms through sudden
geological events. They have been shaped over millions of years by the
slow, orderly process of erosion. They are part of a series of landforms
that naturally erode into other landforms. That series begins with
plateaus, which are relatively level, large expanses of land that rise
some 1,500 feet (457 meters) or more above their surroundings and have at
least one steep side.

A mesa is an isolated, flat-topped hill or mountain with steep sides
that is smaller in area than a plateau. A butte is also a
flat-topped hill with steep sides, though smaller in area than a
mesa
.

Plateaus develop in a few ways, all of which are directly related to the
internal heat forces of Earth. These forces stirring beneath the crust
(the outermost layer of the planet) are responsible for the physical
features on the surface, from mountains to volcanoes to rift valleys and
many others. Earth's internal forces have put pressure on the
bottom of the crust, causing it to fracture into sections. As these
sections, called plates, move about the surface in response to that
pressure, they collide, slide past one another, or slide under each other.
The interaction between the plates or the stress created within a plate as
it has interacted with other plates have brought about the many landforms
defining Earth's surface. The scientific theory explaining the
plates and their movements and interactions is known as plate tectonics.
(For further information on plateau formation and plate tectonics, see the
Plateau
chapter.)

Like all landforms elevated above their surrounding landscapes, a plateau
is prone to erosion. Water, in the form of rain, snow, ice, rivers,
runoff, and groundwater, is the primary force of that erosion. Wind also
plays a part in this erosion, but to a far less degree. Rivers are the
great cutting agents on plateaus. Whether raised with the plateau as it
was elevated or formed afterward, a river will flow downward, seeking out
the level of the body of water into which it drains. And it will do so as
quickly as possible. It will seek out the path of least resistance,
finding areas where rock is weak. Wearing away that rock, the river will
cut downward deeper and
deeper. Over millions of years, a river will form a valley, then a
canyon, separating the plateau into sections. (For more information on
canyon formation, see the
Canyon
chapter.)

On plateaus, areas of weak rock occur along faults, which are cracks or
fractures in Earth's crust. Faults arise when pressure from
underground forces pulls apart or compresses plates, creating stress
within the plate. Faults are common in elevated regions. Rocks along a
fault tend to be weak and broken, and a river or other flowing water
easily cuts through the broken rock. Over time, valleys or canyons form,
and a plateau is further dissected. (For more information on fault
formation, see the
Fault
chapter.)

Rivers erode by picking up sediments (loose rock fragments) and
transporting them to a new location. The speed or velocity at which a
river flows determines the size of the material it can carry. A
fast-moving river carries more sediment and larger material than a
slow-moving one. The sediment acts as an abrasive as it is carried along,
scouring and wearing away the banks and bed (sides and bottom) of the
river. As new material is eroded, the river picks it up. In turn, this new
sediment helps the river cut even deeper into its channel.

From plateaus to mesas to buttes to…

Geologically speaking, no landscape is ever "complete." The
surface of the planet is in constant motion. As new landforms are built
up, others are eroded away. As vast as it may seem, a plateau is
relentlessly carved by erosion. The Colorado Plateau in the four corners
region of the American Southwest is eroding at a rate of 500 vertical feet
every 1 million years. Deep valleys and canyons form steep cliffs that
retreat endlessly as water from storm runoff and streams and rivers washes
away soft rock. Were it not for sections of resistant rock on the surface
of a plateau, the entire landform would wear away over millions of years
to a valley floor.

Those resistant sections allow a plateau to erode into mesas that rise
above the ever-widening valley floor. Mesas maintain their shape because
their cap rock offers protection to the layers of softer rock beneath.
That protection, however, is short-lived. Again, water from storms washes
over the sides of the mesa, wearing them away. As the sides retreat
inward, the overhanging sections of cap rock weaken, fracture, and fall.

As the process of erosion continues, a mesa shrinks in size. Over time, it
becomes a butte, taller than it is wide. Unrelenting, water erodes the
butte as it had the mesa before it and the plateau before that. Capped by
its resistant rock but ever shrinking, the butte may eventually erode into
a pinnacle. This tall, slender tower or spire of rock will stand until it,
too, succumbs to erosion and eventually crumbles to the valley floor.

The Face of Mars

In July 1976, the planetary probe
Viking 1
orbited Mars searching for a potential landing site for a sister probe,
Viking 2
. While photographing areas of the Cydonia region of the planet, the
probe captured an image of a landform that resembled a face with
darkened eyes, a narrow nose, and a frowning mouth. When the National
Aeronautics and Space Administration (NASA) released the image to the
public, it caused a sensation.

NASA scientists reasoned that sunlight on the landform created the
apparent image, but many people thought otherwise. They believed that
the face was artificially created. It was proof, they asserted, that
intelligent life existed on Mars.

More than twenty years after the
Viking 1
probe was released, NASA sent another probe to Mars, the
Mars Global Surveyor
. In early 2001, after having taken tens of thousands of images of the
planet, the
Surveyor
aimed its strong camera lens on the "Face of Mars." This
time, the image clearly showed that the landform was simply another mesa
in an area of mesas and buttes, very much like those that exist in the
American Southwest.

Aerial photograph of a Martian mesa that resembles a human face
.
PHOTOGRAPH REPRODUCED BY PERMISSION OF THE

CORBIS CORPORATION

.

The Enchanted Mesa, in Acoma Pueblo, New Mexico, rises 430 feet from
the desert valley
.
PHOTOGRAPH REPRODUCED BY PERMISSION OF THE

CORBIS CORPORATION

.

Spotlight on famous forms

Enchanted Mesa, New Mexico

In west-central New Mexico stands a mesa made of sandstone, a type of rock
composed of grains of sand bonded together by a mineral cement, like
calcium carbonate. The mesa rises impressively 430 feet (131 meters) above
the surrounding valley. Known as Enchanted Mesa, it was called Mesa
Encantada by Spanish explorers and Katzimo by the Acoma (pronounced
AK-ah-ma), the Native Americans who inhabit the area. The Acoma live in a
pueblo (Native American village) on top of another sandstone mesa located
a few miles away from Enchanted Mesa. The pueblo, believed to have been
founded in the twelfth century, is the oldest continuously inhabited
community in the United States.

According to Acoma legend, Enchanted Mesa is the ancestral home of the
Acoma people. They lived on top of the mesa. One day, when the Acoma were
tending their fields in the surrounding valley, a violent rainstorm arose.
The rain washed away the stairway leading to the top of the mesa, leaving
the elderly and the very young stranded on top. They eventually died from
starvation. Another version of the legend states that only
an old woman and her granddaughter were stranded on top. Rather than face
certain starvation, they leapt to their deaths from the top of the mesa.

Mesa Verde, Colorado

Spanish for "green table," Mesa Verde (pronounced MAY-sah
VURD or VUR-day) is a deeply carved mesa in southwest Colorado. The mesa
is so-named because sagebrush, yucca, and other vegetation cover the area
around it, while pinyon pine and juniper grow on its top. Unlike most
mesas, the top of Mesa Verde is not completely horizontal, but tilts
upward from south to north. Its north side rises nearly 2,000 feet (610
meters) above the valley below. Over millions of years, erosion has carved
out the sides of the mesa. Overhangs and alcoves have developed where
sections of softer sandstone layers have broken away.

Mesa Verde is perhaps more noted as a cultural landscape. Archaeologists
estimate that twenty-four Native American cultures have had some
connection to the area. Prominent among these were the Anasazi, who are
believed to have been the ancestors of the modern Pueblo. For more than
700 years, from approximately 600 to 1300
C.E.
, their culture flourished at Mesa Verde. In the sheltered alcoves
situated high on the mesa's sides, the Anasazi built their
dwellings. Ruins of these elaborate stone structures survive to the
present day. Archaeologists are not quite sure why the Anasazi abandoned
their dwellings abruptly after so many centuries.

Monument Valley, Utah and Arizona

Lying entirely within the Navajo Indian Reservation on the border between
southeastern Utah and northeastern Arizona is Monument Valley. Filled with
striking mesas, buttes, and pinnacles, it is one of the most recognizable
landscapes in the entire American Southwest. Countless Hollywood films
have used the sandy region as a background, from
Stagecoach
(1939) to
Forrest Gump
(1993). More modern advertisements and television commercials are shot in
Monument Valley than anywhere else on Earth.

Part of the Colorado Plateau, Monument Valley spans 2,000 square miles
(5,180 square kilometers). In this flat, desolate landscape, red and
orange landforms rise to heights of 1,000 feet (305 meters) or more. They
are composed primarily of sandstone. Millions of years of erosion on the

Monument Valley, a 2,000-square-mile area on the border of Utah and
Arizona, is filled with mesas, buttes, and canyons. Some of the
freestanding rock formations rise as high 1,000 feet from the desert
floor.
PHOTOGRAPH REPRODUCED BY PERMISSION OF THE

CORBIS CORPORATION

.

sedimentary rock layers of the plateau produced these isolated geological
monuments.

Many of the rock formations in Monument Valley have been given names that
describe their shape: East and West Mitten Buttes, Thunderbird Mesa, and
Totem Pole (pinnacle), among others. The Navajo have occupied the area
since the 1860s. Their history in the region, along with other Native
American cultures, dates back centuries. Ancient ruins, petroglyphs (rock
carvings), and pictographs (rock paintings) have been discovered
throughout the area.

The following is underneath a picture on your site:
Monument Valley, a 2,000-square-mile area on the border of Utah and Arizona, is filled with mesas, buttes, and canyons. Some of the freestanding rock formations rise as high 1,000 feet from the desert floor. PHOTOGRAPH REPRODUCED BY PERMISSION OF THE CORBIS CORPORATION

Unfortunately, the picture has nothing to do with Monument Valley - it is of a formation a couple hundred miles away in Sedona, AZ - Cathedral Rock!

Just got back from Big Bend, Texas and Davis Mountains. Couldn't figure out why all those (buttes?) had 'tops' that seemed to all be at the same height. This just explained everything I saw in ten minutes. Thanks!

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